During the normal storage and usage of automotive and industrial lubricants, the lubricants are subject to high temperatures and oxygen which can lead to oxidation of the lubricants. Oxidized lubricants can cause the build up of oil-soluble acids, lacquers and sludge which can promote premature deterioration of engines and other lubricated systems.
Another problem associated with mechanical systems relates to the frictional forces created between relatively moving metal parts which can cause the wearing away of metal surfaces. An ability to reduce the coefficient of friction between these metal surfaces is not an inherent property of all lubricants.
Additionally, it is often found that lubricants are corrosive to certain metals, typically iron, copper, aluminum and lead, which are found in engines.
Additives are often blended with lubricants to inhibit oxidation of the lubricant as well as to prevent the wear and corrosion of metal parts. Phosphorodithioate compositions, i.e., the metal salts of phosphorodithioates, such as zinc dialkylphosphorodithioates, have been widely reported as multifunctional antiwear, peroxide decomposing and bearing corrosion inhibiting additives for industrial fluids. Further, organic phosphonates such as dibutyl hydrogen phosphonates and dioleyl hydrogen phosphonates have been described as antiwear and extreme pressure additives for lubricants.